Innate resistance linked to non-enzymatic biochemical alteration of rice plants in response to Pyricularia oryzae

Blast disease of rice caused by the fungus Pyricularia oryzae Cavara is one of the most destructive diseases, which causes about 10% to 30% yield loss. Utilization of innate host resistance has been the best way to manage the disease, for which understanding the innate immunity of our popular rice genotypes is necessary. To measure non-enzymatic biochemical alterations of rice genotypes against P. oryzae, an experiment was conducted and repeated once in the next year following a factorial completely randomized design at Plant Protection and Plant Breeding laboratory of Agrotechnology Discipline of Khulna University. BRRI dhan74, BRRI dhan33 and BRRI dhan75 along with IR 64 (resistant check line) showed minimum disease incidence (%) and maximum synthesis of total flavonoids, antioxidants, protein and sugar. These genotypes also maintained a balanced ROS (H2O2; O2-) production at later disease developmental stages (96 and 120 HAI). Pearson correlation revealed that H2O2 and O2- were positively, whereas antioxidant, flavonoid, protein and sugar was negatively associated with disease incidence. Principal component analysis (PCA) showed 91.7% total variability and indicated that total antioxidant, flavonoid, protein, sugar and H2O2 contributed more to the variation. Notably, BRRI dhan74, BRRI dhan33 and BRRI dhan75 sustained higher synthesis levels of resistance-related non-enzymatic compounds with lower disease incidence indicating a robust defense response against P. oryzae.